1. Field of the Invention
The present invention relates to a laser scanning apparatus, and more particularly, to a laser scanning apparatus in which a beam emitted from an optical source is deflected by a scan disk having a plurality of diffraction patterns formed thereon, and projected onto a scanning object such as a photoreceptor drum via a light path changing unit.
2. Description of the Related Art
FIG. 1 shows a laser scanning apparatus adopted in a conventional electrophotographic printer. The laser scanning apparatus includes an optical source 11 and a scan disk 14. Reference numeral 12 denotes a cylindrical lens, and reference numerals 13, 15 and 16 denote optical elements for changing a light path and controlling the size of a beam. The scan disk 14 is segmented into a plurality of areas on which diffraction patterns for deflecting an incident beam are formed.
A beam emitted from the optical source 11 is deflected by the scan disk 14 which is rotated by a motor (not shown), and projected onto a photoreceptor drum 17 via the optical elements 15 and 16. The light beam repeatedly scans the photoreceptor drum 17 corresponding to the diffraction patterns formed on the scan disk 14.
In the laser scanning apparatus, the scan disk 14 deflects an incident beam in a desired direction, but transmits or reflects some of the incident beam in an undesired direction. The traveling path of the beam emitted from the scan disk 14 in the undesired direction may be changed and finally reach the photoreceptor drum 17 in the laser scanning apparatus. This causes an image forming error.
High-speed rotation of the scan disk 14 is required to increase the scanning speed, which generates noise.